Trent Lister, 29, bought his investment property in Norlane, Geelong with his partner and his mother, but what started as a long-term life plan has descended into a nightmare.

Earlier this month, during a routine inspection of the property, Mr Lister arrived to find his property had been turned into a cannabis crop house by new tenants who had only been in the property for a few months.

The home was left trashed, the electricity had been rewired, holes cut in floors and the roof, and cupboards removed.

The bath was being used to send water to different parts of the house and the occupants had even turned the doors around to make more space in the bedrooms.

The damage bill is estimated in the thousands and Mr Lister said he was facing bankruptcy after insurance complications.

His mother, who is a foster carer looking after four children, is now also in financial strife.

"When that door opened, my heart just sank," he said.

"You wouldn't believe it unless you saw it. It's amazing how sophisticated these people are at what they do because they're probably going to get away with it."

Those responsible vanished, and while Mr Lister is hopeful they will be caught, he is not holding his breath.

"[Police] don't think they'll catch them," he said.

Officers took DNA from the house and are running checks to see if they have any matches in the system.